This invention relates to attenuators for optical radiation and, more particularly, to a new and improved attenuator especially adapted to attenuate laser radiation.
Laser radiation has been employed increasingly in science and technology, particularly since lasers with high radiation output capacity, such as the CO.sub.2 laser, have become available. In many cases it is necessary to adjust the intensity of laser radiation emitted by such a high intensity source in accordance with the intended use.
Inasmuch as control of the output of a laser presents certain problems, external radiation absorbers have heretofore been used to adjust radiation intensity. For example, quartz or glass plates are provided with an absorbing coloring or coating which is as nearly neutral as possible. Such grey filter plates, however, are not neutral over a broad wavelength band. That is, the absorption depends upon the wavelength of the radiation transmitted. Moreover, such filter plates introduce disturbances due to interference of rays reflected from the front and the back surfaces as well as wave front distortion resulting from irregularities in the front and back surfaces and the spacing between them, especially when the absorber plate becomes hot.